WO1994023478A2 - Q-switched laser system, in particular for laser lithotripsy - Google Patents

Q-switched laser system, in particular for laser lithotripsy Download PDF

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Publication number
WO1994023478A2
WO1994023478A2 PCT/DE1994/000362 DE9400362W WO9423478A2 WO 1994023478 A2 WO1994023478 A2 WO 1994023478A2 DE 9400362 W DE9400362 W DE 9400362W WO 9423478 A2 WO9423478 A2 WO 9423478A2
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WO
WIPO (PCT)
Prior art keywords
laser system
laser
switched laser
switched
optical
Prior art date
Application number
PCT/DE1994/000362
Other languages
German (de)
French (fr)
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WO1994023478A3 (en
Inventor
Gerhard Müller
Pavel Pashinin
Original Assignee
Clyxon Laser Für Mediziner Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE19934310023 external-priority patent/DE4310023A1/en
Application filed by Clyxon Laser Für Mediziner Gmbh filed Critical Clyxon Laser Für Mediziner Gmbh
Priority to EP94911094A priority Critical patent/EP0691043B1/en
Priority to DE59403398T priority patent/DE59403398D1/en
Publication of WO1994023478A2 publication Critical patent/WO1994023478A2/en
Publication of WO1994023478A3 publication Critical patent/WO1994023478A3/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
    • A61B18/20—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser
    • A61B18/22—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor
    • A61B18/26—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor for producing a shock wave, e.g. laser lithotripsy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
    • H01S3/109—Frequency multiplication, e.g. harmonic generation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1123—Q-switching
    • H01S3/113—Q-switching using intracavity saturable absorbers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08013—Resonator comprising a fibre, e.g. for modifying dispersion or repetition rate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08059—Constructional details of the reflector, e.g. shape

Definitions

  • the invention relates to a Q-switched laser system of the type specified in the preamble of claim 1 and claim 2.
  • Solid-state laser systems are known from the publications WO 90/12544, WO 90/04358, WO 91/05332 and AT-B-380634 known as laser lithotripsy.
  • the fiber transmitting the energy to the application site very quickly destroys itself due to the short pulse lengths used there.
  • the technical structures of these laser systems are very cost-intensive and maintenance-intensive.
  • the invention is therefore based on the object of specifying a quality-switched laser system of the type mentioned at the outset which, especially for laser lithotripsy, does not produce laser pulses which lead to premature wear of the transmission fibers, works efficiently and can be produced economically .
  • the pulse duration for the optimal inclusion condition in nanoseconds corresponds to 1.5 times the diameter of the energy-applying fibers in micrometers.
  • the optimal pulse duration for lithotripsy is approximately 600 to 650 ns.
  • the invention thus includes the idea of designing the generic laser system in such a way that it delivers corresponding pulses whose length, depending on the application fiber used, is in particular between 200 ns and 1 ⁇ s, possibly up to a few ⁇ s.
  • preferred laser-active media such as neodymium-doped laser crystals, in particular Nd.YAG and Nd: YAI0 3 in normal Q-switched operation, however, they only have pulse lengths between 7 and 15 ns.
  • this limitation is overcome by an optical extension of the resonator using a long optical waveguide. (For a pulse length of approx. 650 ns, a resonator extension using an optical waveguide of approx. 18 m length is typically necessary.)
  • This measure has the effect that the pulse length of the laser system can be varied in a wide range as a function of the length of the waveguide - in particular between 200 ns and a few ⁇ s - and not only in a cost-effective manner, without the output pulse power changing significantly (Variations ⁇ 10% were found), but that at the same time a smoothing of the disadvantageous statistical intensity oscillations leading to increased fiber wear during a laser pulse (the so-called "spikes”) and also a homogenization of the spatial intensity profile in the case of suppression ⁇ kink of intensity increases in the beam cross section (so-called "hot spots”) is achieved.
  • the thus generated generation of spatially and temporally smoothed pulse profiles is of considerable advantage for the transmission of the pulses through coupled external optical waveguides. In particular, it significantly increases their lifespan.
  • the invention includes the idea that the laser-active medium with a higher than that for the generation of
  • bursts Pulse cascades
  • FIG. 1 a shows a schematic illustration of a laser system according to one embodiment of the invention
  • FIG. 1b shows a schematic illustration of the main optical components of a laser system according to an embodiment of the invention modified compared to FIG.
  • FIG. 2a shows the schematic representation of the beam path in a multipass waveguide as part of a further embodiment of the invention
  • Figure 2b is a schematic representation of the embodiment containing the multipass waveguide.
  • FIG. 1 a shows schematically a preferred optical arrangement of a long-pulse solid-state lithotripsy laser as an embodiment of the invention.
  • an assembly 1 consists of a focusing lens 1.3, a fiber optic resonator extension 1.2 and a curved resonator end mirror 1.1, the curvature and distance of which from the fiber exit of the resonator extension (1.2) is dimensioned such that taking into account the numerical aperture of the fiber, the radius of curvature corresponds to approximately half the distance between the fiber end surface and the mirror surface.
  • An assembly 2 contains a conventional laser cavity.
  • 2.1 denotes a laser crystal, preferably Nd: YAG or Nd: YA103, 2.2 a flash lamp for optical pumping and 2.3 a unit for energy supply and system control.
  • An assembly 3 contains a partially transparent resonator end mirror 3.4, a nonlinear crystal 3.3 for frequency doubling, typically a KTP crystal, and a passive Q switch 3.2, typically Cr 4+: YAG or LiF (F2-), and relay optics 3.1 to collimate the radiation.
  • a further increase can be achieved by inserting a polarization-optical assembly, consisting of a Brewster angle polarizer and a retroreflector arranged essentially at right angles thereto, between either components 1.2 and 1.3 of assembly 1 or components 3.2 and 3.3 of assembly 3 the efficiency for generating the first harmonics can be achieved.
  • the following typical output values can be achieved with a pump energy on the flash lamp of approximately 30 J: pulse duration, adjustable between 200 ns and 1 ⁇ s, depending on the length of the fiber extension in the resonator, with approx. 20 m fiber length 160 mJ at 1064 nm basic mission and approx. 15 mJ at 532 nm (2nd harmonic), based on a basic absorption of the passive Q-switch of about 25%.
  • pulse duration adjustable between 200 ns and 1 ⁇ s, depending on the length of the fiber extension in the resonator, with approx. 20 m fiber length 160 mJ at 1064 nm basic mission and approx. 15 mJ at 532 nm (2nd harmonic), based on a basic absorption of the passive Q-switch of about 25%.
  • the output energy of the 2nd harmonic increases to approximately 22 to 25 mJ.
  • the core diameter of the resonator extension is only 280 ⁇ m, so that taking into account the divergence caused by the numerical aperture, the transfer of the total energy delivered through a Q / Q fiber 4 with a core diameter of 360 ⁇ m to the lithotripsy a stone 5 is possible.
  • a further increase in the destruction efficiency in lithotripsy is achieved in that the laser crystal is excited with a pump energy that is higher than that required to generate individual pulses.
  • a pump energy that is higher than that required to generate individual pulses.
  • the increase by 30%, ie to approx. 40 J results in the emission of a cascade of individual pulses, the time interval of which is approximately 50 ⁇ s with a basic absorption of the Q-switch at 25% and the time interval when the Basic absorption can be halved by a factor of about 2.
  • This pulse cascade also called burst
  • telbar can be used to generate sequential compression surges.
  • An embodiment of the arrangement described above is also possible as a solid-state laser with an erbium-doped laser crystal which, depending on the host crystal or matrix, emits wavelengths between 1.54 and 2.94 ⁇ m.
  • the following laser media can be used in particular: Erbium: YAG, Erbium: YSGG, Erbium: YAG coded with chromium and thulium, so-called CTE lasers.
  • a zirconium fluoride fiber or an aluminum fluoride fiber is used as the preferred waveguide.
  • Erbiu glass lasers based on chalcogenide glasses e.g. germanium, arsenic, sulfur glasses
  • fibers made from the same chalcogenide glass can be used as waveguides.
  • Optical crystals such as e.g. Lithium niobate or lithium iodate used.
  • other quality switches known as such can also be used.
  • optical waveguide is provided at both ends with a taper coupler (a coupling layer tapering in a wedge or trumpet shape in cross section).
  • Fig. Lb shows such, compared to the arrangement of Fig. La in the sequence of laser crystal 2.1 and Waveguide 1.2 between mirror 1.1 and Q-switch 3.2 and partially transparent mirror 3.4 and in the formation of the laser crystal as an erbium-doped crystal
  • holmium-doped solid-state lasers as well as solid-state lasers with frequency multiplication in the blue and ultraviolet spectral range and pulsed gas lasers, such as e.g. Excimer laser and nitrogen laser can be realized.
  • a planar optical waveguide can also be used as a multi-pass reflection plate instead of the optical fiber.
  • An embodiment of such a planar multipass waveguide 1.21 is shown in FIG. 2a.
  • this waveguide essentially has the shape of a flat cuboid or a plate which is provided with a coupling-in / coupling-out section 1.22 and the large optical path length of the beam by multiple beam reflection under reflection from the walls ⁇ gene of the cuboid is realized.
  • FIG. 2b shows a configuration of the optical part of the laser system which largely corresponds to the arrangement shown in FIG. 1b, using a multipass wave conductor 1.21 of the type shown in Fig. 2a instead of the wound fiber waveguide 1.2 shown in Fig. lb. All other elements correspond to those in FIG. 1b and are therefore not explained again.
  • chalcogenide glasses of a suitable composition e.g. germanium arsenic, sulfur
  • a suitable composition e.g. germanium arsenic, sulfur
  • highly transparent crystals such as e.g. Sapphire or yttrium aluminum garnet or other host crystals of the respective laser media or e.g. silicon, germanium or zinc selenide are also used.

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Abstract

A Q-switched laser system, in particular for laser lithotripsy, has a laser-active medium (2.1) in a resonator, an optical pumping arrangement (2.3) and a passive Q-switch (3.2). A resonator extension (1.2) having an optical waveguide is associated to the laser-active medium (2.1) in order to increase the laser pulse length.

Description

Gütegeschaltetes Lasersystem, insbesondere für die Q-switched laser system, especially for the
LaserlithotripsieLaser lithotripsy
B e s c h r e i b u n gDescription
Die Erfindung betrifft ein gütegeschaltetes Lasersystem der im Oberbegriff des Anspruchs 1 sowie des Anspruchs 2 angegebenen Art.The invention relates to a Q-switched laser system of the type specified in the preamble of claim 1 and claim 2.
Aus den Druckschriften WO 90/12544, WO 90/04358, WO 91/05332 und AT-B-380634 sind Festkörperlasersysteme für die Laserlithotripsie bekannt. Bei diesen Systemen, die mit kurzen Einzelimpulsen arbeiten, zerstört sich auf¬ grund der dort verwendeten kurzen Pulslängen die die Ener- gie zum Applikationsort übertragende Faser im praktischen Gebrauch sehr schnell selbst. Darüber hinaus sind die technischen Aufbauten dieser Lasersysteme sehr kosten- und wartungsinteniv.Solid-state laser systems are known from the publications WO 90/12544, WO 90/04358, WO 91/05332 and AT-B-380634 known as laser lithotripsy. In these systems, which work with short individual pulses, the fiber transmitting the energy to the application site very quickly destroys itself due to the short pulse lengths used there. In addition, the technical structures of these laser systems are very cost-intensive and maintenance-intensive.
Überdies hat es sich bei experimentellen Untersuchungen als günstig herausgestellt, bei der Laserlithotripsie mit einem sogenannten Doppelpuls zu arbeiten, bei dem zwei Im¬ pulse kurz hintereinander zum Applikationsort übertragen werden, wobei der eine Puls zum eigentlichen energietra¬ genden Puls zum kurzwelligen Bereich hin ("blau") ver- schoben ist, typischerweise die Harmonische der Grundwel¬ lenlänge darstellt. Diese Kombination erlaubt ein frühzei¬ tiges Zünden des optischen Durchbruchs (Plasma) an der zu zerstörenden Steinoberfläche und ermöglicht damit einen höheren Wirkungsgrad bei der Steinzertrümmerung. Aller- dings tritt auch hierbei der Nachteil eines schnellen Fa¬ serabbrandes im praktischen Einsatz auf.In addition, it has been found to be advantageous in experimental investigations to work with laser lithotripsy with a so-called double pulse, in which two pulses are transmitted in quick succession to the application site, with one pulse towards the actual energy-carrying pulse towards the short-wave range (" blue ") is shifted, typically represents the harmonic of the fundamental wavelength. This combination allows the optical breakthrough (plasma) to be ignited at the stone surface to be destroyed at an early stage and thus enables a higher degree of efficiency in the destruction of the stone. However, here too there is the disadvantage of rapid fiber burn-up in practical use.
Der Erfindung liegt daher die Aufgabe zugrunde, ein güte¬ geschaltetes Lasersystem der eingangs genannten Gattung anzugeben, das besonders für die Laserlithotripsie geeig¬ nete, nicht zu einem vorzeitigen Verschleiß der Übertra¬ gungsfasern führende, Laserimpulse erzeugt, effizient ar¬ beitet und kostengünstig herstellbar ist.The invention is therefore based on the object of specifying a quality-switched laser system of the type mentioned at the outset which, especially for laser lithotripsy, does not produce laser pulses which lead to premature wear of the transmission fibers, works efficiently and can be produced economically .
Diese Aufgabe wird durch ein Lasersystem mit den Merkmalen des Anspruchs 1 bzw. des Anspruchs 2 gelöst. Ausgehend von dem bekannten Stand der Technik hat sich überraschenderweise gezeigt, daß die Effizienz der Stein¬ zertrümmerung bei der Laserlithotripsie nicht nur vom frü¬ hestmöglichen Zünden eines Plasmas und der dadurch entste- henden Stoßwelle und der Erzeugung von Kavitationsblasen abhängt, sondern entscheidend durch die Erfüllung einer Einschlußbedingung für das Plasma mit nachfolgendem Ver- dichtungsstoß bestimmt ist.This object is achieved by a laser system with the features of claim 1 and claim 2. Based on the known state of the art, it has surprisingly been found that the efficiency of stone crushing in laser lithotripsy depends not only on the earliest possible ignition of a plasma and the resulting shock wave and the generation of cavitation bubbles, but crucially on its fulfillment an inclusion condition for the plasma with subsequent compression shock is determined.
Theoretische und experimentelle Untersuchungen der Erfin¬ der konnten überraschenderweise bestätigen, daß optimale Einschlußbedingungen unter Berücksichtigung der Laufzeit der akustischen Stoßwellen bei Einhaltung bestimmter Ver¬ hältnisse zwischen der Impulsdauer und der Geometrie der Endfläche der die Energie zum Applkationsort übertragenden Faser selbst gegeben sind. Als Faustregel wurde gefunden, daß die Pulsdauer für die optimale Einschlußbedingung in Nanosekunden dem l,5fachen des Durchmessers der energie- applizierenden Fasern in Mikrometern entspricht. Das heißt also beispielsweise, bei einer Q/Q-Faser mit 360 μm Kern, die - je nach Hersteller - einen Durchmesser am optischen Cladding von etwa 400 bis 420 μm besitzt, ist die optimale Pulsdauer für die Lithotripsie ca. 600 bis 650 ns.Theoretical and experimental investigations of the inventors surprisingly confirmed that optimal inclusion conditions are given, taking into account the propagation time of the acoustic shock waves, while maintaining certain ratios between the pulse duration and the geometry of the end face of the fiber itself which transfers the energy to the application site. As a rule of thumb, it was found that the pulse duration for the optimal inclusion condition in nanoseconds corresponds to 1.5 times the diameter of the energy-applying fibers in micrometers. For example, for a Q / Q fiber with a 360 μm core, which - depending on the manufacturer - has a diameter on the optical cladding of approximately 400 to 420 μm, the optimal pulse duration for lithotripsy is approximately 600 to 650 ns.
Die Erfindung schließt somit den Gedanken ein, das gat¬ tungsgemäße Lasersystem so auszubilden, daß es entspre¬ chende Impulse liefert, deren Länge - je nach verwendeter Applikationsfaser - insbesondere zwischen 200 ns und 1 μs, ggf. bis zu einigen μs, liegt. Herkömmliche und aus Ko- stengründen zu bevorzugende laseraktive Medien wie neodym¬ dotierte Laserkristalle, insbesondere Nd.YAG und Nd:YAI03 haben im normalen gütegeschalteten Betrieb allerdings le¬ diglich Pulslängen zwischen 7 und 15 ns.The invention thus includes the idea of designing the generic laser system in such a way that it delivers corresponding pulses whose length, depending on the application fiber used, is in particular between 200 ns and 1 μs, possibly up to a few μs. Conventional and for cost reasons preferred laser-active media such as neodymium-doped laser crystals, in particular Nd.YAG and Nd: YAI0 3 in normal Q-switched operation, however, they only have pulse lengths between 7 and 15 ns.
Erfindungsgemäß wird diese Limitierung durch eine optische Verlängerung des Resonators mittels eines langen optischen Wellenleiters überwunden. (Für eine Pulslänge von ca. 650 ns ist typischerweise eine Resonatorverlängerung mittels eines optischen Wellenleiters von ca. 18 m Länge notwen¬ dig. )According to the invention, this limitation is overcome by an optical extension of the resonator using a long optical waveguide. (For a pulse length of approx. 650 ns, a resonator extension using an optical waveguide of approx. 18 m length is typically necessary.)
Durch diese Maßnahme wird der Effekt erzielt, daß nicht nur auf kostengünstige Weise die Pulslänge des Lasersy- stems in weiten Bereichen in Abhängigkeit von der Länge des Wellenleiters veränderbar ist - insbesondere zwischen 200 ns und einigen μs - , ohne daß sich die abgegebene Pulsspitzenleistung wesentlich ändert (festgestellt wurden Variationen < 10 %), sondern daß gleichzeitig eine Glät¬ tung der nachteiligen, zu erhöhtem Faserverschleiß führen¬ den, statistischen Intensitätsoszillationen während eines Laserpulses (der sog. "Spikes") und weiterhin eine Homoge¬ nisierung des räumlichen Intensitätsprofils bei Unterdrüc¬ kung von Intensitätsüberhöhungen im Strahlquerschnitt (sog. "Hot Spots") erreicht wird. Die somit bewirkte Er¬ zeugung räumlich und zeitlich geglätteter Impulsprofile ist von erheblichem Vorteil für die Übertragung der Impul¬ se durch angekoppelte, externe Lichtwellenleiter. Sie er¬ höht insbesondere deren Lebensdauer wesentlich.This measure has the effect that the pulse length of the laser system can be varied in a wide range as a function of the length of the waveguide - in particular between 200 ns and a few μs - and not only in a cost-effective manner, without the output pulse power changing significantly (Variations <10% were found), but that at the same time a smoothing of the disadvantageous statistical intensity oscillations leading to increased fiber wear during a laser pulse (the so-called "spikes") and also a homogenization of the spatial intensity profile in the case of suppression ¬ kink of intensity increases in the beam cross section (so-called "hot spots") is achieved. The thus generated generation of spatially and temporally smoothed pulse profiles is of considerable advantage for the transmission of the pulses through coupled external optical waveguides. In particular, it significantly increases their lifespan.
Weiter schließt die Erfindung den Gedanken ein, das laser- aktive Medium mit einer höheren als der zur Erzeugung vonFurthermore, the invention includes the idea that the laser-active medium with a higher than that for the generation of
Einzelimpulsen erforderlichen Pumpenergie anzuregen, womit Impulskaskaden ("Bursts) erzeugt werden können, die - ent¬ sprechend den oben dargelegten Wirkungsbedingungen der Laserimpulsstrahlung bei der Laserlithotripsie - Wirkungs¬ vorteile gegenüber Einzelimpulsen haben.To stimulate individual pulses required pump energy, with what Pulse cascades ("bursts") can be generated which - in accordance with the above-described conditions of action of laser pulse radiation in laser lithotripsy - have advantages in relation to individual pulses.
Vorteilhafte Weiterbildungen der Erfindung sind in den Un¬ teransprüchen gekennzeichnet bzw. werden nachstehend zu¬ sammen mit der Beschreibung der bevorzugten Ausführung der Erfindung anhand der Figuren näher dargestellt. Es zeigen:Advantageous developments of the invention are characterized in the subclaims or are shown in more detail below together with the description of the preferred embodiment of the invention with reference to the figures. Show it:
Figur la eine schematische Darstellung eines Lasersystems nach einer Ausführungsform der Erfindung,FIG. 1 a shows a schematic illustration of a laser system according to one embodiment of the invention,
Figur lb eine schematische Darstellung der optischen Haupt-Komponenten eines Lasersystems nach einer gegenüber Figur la abgewandelten Ausführungsform der Erfindung,FIG. 1b shows a schematic illustration of the main optical components of a laser system according to an embodiment of the invention modified compared to FIG.
Figur 2a die schematische Darstellung des Strahlenganges in einem Multipass-Wellenleiter als Bestandteil einer wei- teren Ausführungsform der Erfindung undFIG. 2a shows the schematic representation of the beam path in a multipass waveguide as part of a further embodiment of the invention and
Figur 2b eine schematische Darstellung der den Multipass- Wellenleiter enthaltenden Ausführungsform.Figure 2b is a schematic representation of the embodiment containing the multipass waveguide.
Fig. la zeigt schematisch eine bevorzugte optische Anord¬ nung eines Langpuls-Festkörperlithotripsielasers als Aus¬ führungsform der Erfindung. Hierbei besteht eine Baugruppe 1 aus einer Fokusierlinse 1.3, einer faseroptischen Reso¬ natorverlängerung 1.2 und einem gewölbten Resonatorend- spiegel 1.1, dessen Wölbung und Abstand zum Faseraustritt der Resonatorverlängerung (1.2) derart bemessen ist, daß unter Berücksichtigung der numerischen Apertur der Faser der Krümmungsradius etwa dem halben Abstand zwischen Fase¬ rendfläche und Spiegeloberfläche entspricht.FIG. 1 a shows schematically a preferred optical arrangement of a long-pulse solid-state lithotripsy laser as an embodiment of the invention. Here, an assembly 1 consists of a focusing lens 1.3, a fiber optic resonator extension 1.2 and a curved resonator end mirror 1.1, the curvature and distance of which from the fiber exit of the resonator extension (1.2) is dimensioned such that taking into account the numerical aperture of the fiber, the radius of curvature corresponds to approximately half the distance between the fiber end surface and the mirror surface.
Eine Baugruppe 2 beinhaltet eine herkömmliche Laserkavi- tät. Dabei bezeichnet 2.1 einen Laserkristall, vorzugswei¬ se Nd:YAG oder Nd:YA103, 2.2 eine Blitzlampe zum optischen Pumpen und 2.3 eine Einheit zur Energieversorgung und Sy¬ stemsteuerung.An assembly 2 contains a conventional laser cavity. 2.1 denotes a laser crystal, preferably Nd: YAG or Nd: YA103, 2.2 a flash lamp for optical pumping and 2.3 a unit for energy supply and system control.
Eine Baugruppe 3 beinhaltet einen teiltransparenten Reso¬ nator-Endspiegel 3.4, einen nichtlinearen Kristall 3.3 zur FrequenzVerdopplung, typischerweise einen KTP-Kristall, sowie einen passiven Güteschalter 3.2, typischerweise Cr 4+:YAG bzw. LiF(F2-), und eine Relaisoptik 3.1 zur Kolli- ierung der Strahlung.An assembly 3 contains a partially transparent resonator end mirror 3.4, a nonlinear crystal 3.3 for frequency doubling, typically a KTP crystal, and a passive Q switch 3.2, typically Cr 4+: YAG or LiF (F2-), and relay optics 3.1 to collimate the radiation.
In Weiterführung des Erfindungsgedankens kann durch Einfü¬ gen einer polarisationsoptischen Baugruppe, bestehend aus einem Brewster-Winkelpolarisator und einem im wesentlichen rechtwinklig hierzu angeordneten Retroreflektor, zwischen entweder den Bauelementen 1.2 und 1.3 der Baugruppe l oder den Bauelementen 3.2 und 3.3 der Baugruppe 3 eine weitere Steigerung der Effizienz zur Erzeugung der ersten Harmoni- sehen erreicht werden.In a continuation of the inventive concept, a further increase can be achieved by inserting a polarization-optical assembly, consisting of a Brewster angle polarizer and a retroreflector arranged essentially at right angles thereto, between either components 1.2 and 1.3 of assembly 1 or components 3.2 and 3.3 of assembly 3 the efficiency for generating the first harmonics can be achieved.
Für das bevorzugte Ausführungsbeispiel lassen sich, ausge¬ hend von einem neodymdotierten YAG-Laserkristall von 5 mm Durchmesser und 5 cm Länge, bei einer Pumpenergie an der Blitzlampe von ca. 30 J folgende typische Ausgangswerte erreichen: Pulsdauer, einstellbar zwischen 200 ns und l μs, abhängig von der Länge der Faserverlängerung im Reso¬ nator, bei ca. 20 m Faserlänge 160 mJ bei 1064 nm Grunde¬ mission und ca. 15 mJ bei 532 nm (2. Harmonische), ausge- hend von einer Grundabsorption des passiven Güteschalters von ca. 25 %. Dabei ändert sich bei Variationen der Puls¬ länge von 200 ns bis l μs die Ausgangsenergie lediglich um ca. 10 %. Bei Verwendung von polarisierter Laserstrah¬ lung, entweder durch Hinzufügen der oben erwähnten zusätz¬ lichen Elemente oder durch Verwendung eines doppelbrechen- den Lasermaterials, wie beispielsweise Nd:YAl03, erhöht sich die Ausgangsenergie der 2. Harmonischen auf ca. 22 bis 25 mJ. Dabei beträgt der Kerndurchmesser der Resona¬ torverlängerung lediglich 280 μm, so daß unter Berücksich¬ tigung der durch die numerische Apertur bedingten Diver- genz die Übertragung der insgesamt abgegebenen Energie durch eine Q/Q-Faser 4 mit 360 μm Kerndurchmesser zur Lit¬ hotripsie an einem Stein 5 möglich ist.For the preferred embodiment, starting from a neodymium-doped YAG laser crystal of 5 mm in diameter and 5 cm in length, the following typical output values can be achieved with a pump energy on the flash lamp of approximately 30 J: pulse duration, adjustable between 200 ns and 1 μs, depending on the length of the fiber extension in the resonator, with approx. 20 m fiber length 160 mJ at 1064 nm basic mission and approx. 15 mJ at 532 nm (2nd harmonic), based on a basic absorption of the passive Q-switch of about 25%. With variations in the pulse length from 200 ns to 1 μs, the output energy changes only by approximately 10%. When using polarized laser radiation, either by adding the above-mentioned additional elements or by using a birefringent laser material, such as Nd: YAl0 3 , the output energy of the 2nd harmonic increases to approximately 22 to 25 mJ. The core diameter of the resonator extension is only 280 μm, so that taking into account the divergence caused by the numerical aperture, the transfer of the total energy delivered through a Q / Q fiber 4 with a core diameter of 360 μm to the lithotripsy a stone 5 is possible.
Erfindungsgemäß wird eine weitere Steigerung der Zerstö- rungseffizienz bei Lithotripsie dadurch erreicht, daß der Laserkristall mit einer höheren als zur Erzeugung von Ein¬ zelpulsen notwendigen Pumpenergie angeregt wird. Bereits die Erhöhung um 30 %, also auf ca. 40 J, hat die Emission einer Kaskade von Einzelimpulsen zur Folge, deren zeitli- eher Abstand bei einer Grundabsorption des Güteschalters von 25 % bei ca. 50 μs liegt und deren zeitlicher Abstand bei Erhöhung der Grundabsorpion um den Faktor 2 etwa halbiert werden kann. Diese Impulskaskade (auch Burst ge¬ nannt), führt zu einer wesentlichen Steigerung der Zerstö- rungseffizienz am Stein 5 bei der Lithotripsie, da durch die optimierten Einschlußbedingungen die Folgepulse unmit- telbar zur Erzeugung von sequentiellen Verdichtungsstößen genutzt werden können.According to the invention, a further increase in the destruction efficiency in lithotripsy is achieved in that the laser crystal is excited with a pump energy that is higher than that required to generate individual pulses. Already the increase by 30%, ie to approx. 40 J, results in the emission of a cascade of individual pulses, the time interval of which is approximately 50 μs with a basic absorption of the Q-switch at 25% and the time interval when the Basic absorption can be halved by a factor of about 2. This pulse cascade (also called burst) leads to a significant increase in the destruction efficiency at stone 5 in lithotripsy, since the subsequent pulses immediately result from the optimized inclusion conditions. telbar can be used to generate sequential compression surges.
Eine Ausführung der oben beschriebenen Anordnung ist auch als Festkörperlaser mit einem Erbium-dotierten Laserkri¬ stall, der je nach Wirtskristall bzw. Matrix Wellenlängen zwischen 1,54 und 2,94 μm emittiert, möglich. Dabei können insbesondere folgende Lasermedien zur Anwendung gelangen: Erbium:YAG, Erbium:YSGG, Erbium:YAG kodotiert mit Chrom und Thulium, sog. CTE-Laser. Als bevorzugter Wellenleiter kommt hierbei eine Zirkonfluoridfaser oder eine Aluminium¬ fluoridfaser zur Anwendung.An embodiment of the arrangement described above is also possible as a solid-state laser with an erbium-doped laser crystal which, depending on the host crystal or matrix, emits wavelengths between 1.54 and 2.94 μm. The following laser media can be used in particular: Erbium: YAG, Erbium: YSGG, Erbium: YAG coded with chromium and thulium, so-called CTE lasers. A zirconium fluoride fiber or an aluminum fluoride fiber is used as the preferred waveguide.
In Weiterbildung dieser Ausführung gelangen auch Erbiu - Glaslaser auf der Basis von Chalkogenidgläsern (z.B. Germanium-, Arsen-, Schwefelgläsern) zur Anwendung, wobei als Wellenleiter Fasern aus dem gleichen Chalkogenidglas verwendet werden können.In a further development of this version, Erbiu glass lasers based on chalcogenide glasses (e.g. germanium, arsenic, sulfur glasses) are used, whereby fibers made from the same chalcogenide glass can be used as waveguides.
Als passiver Güteschalter werden optische Kristalle, wie z.B. Lithium-Niobat bzw. Lithium-Jodat, verwendet. Es kön¬ nen aber auch andere als solche bekannte Güteschalter ein¬ gesetzt werden.Optical crystals such as e.g. Lithium niobate or lithium iodate used. However, other quality switches known as such can also be used.
Auf die Verwendung von Linsen zur Strahlkonfektionierung innerhalb des Resonators kann verzichtet werden, wenn der optische Wellenleiter an beiden Enden mit einem Taper- Koppler (einer im Querschnitt in etwa keil- oder trompe- tenförmig zulaufenden Einkopplungsschicht) versehen ist.The use of lenses for beam assembly within the resonator can be dispensed with if the optical waveguide is provided at both ends with a taper coupler (a coupling layer tapering in a wedge or trumpet shape in cross section).
Fig. lb zeigt eine solche, gegenüber der Anordnung nach Fig. la weiterhin in der Abfolge von Laserkristall 2.1 und Wellenleiter 1.2 zwischen Spiegel 1.1 und Güteschalter 3.2 sowie teildurchlässigem Spiegel 3.4 und in der Ausbildung des Laserkristalls als Erbium-dotierter Kristall abwei-Fig. Lb shows such, compared to the arrangement of Fig. La in the sequence of laser crystal 2.1 and Waveguide 1.2 between mirror 1.1 and Q-switch 3.2 and partially transparent mirror 3.4 and in the formation of the laser crystal as an erbium-doped crystal
•» chende, Konfiguration mit zwei Tapern 1.5, die als koni- sehe Endstücke mit dem faseroptischen Wellenleiter 1.2 ge¬ spleißt sind.• Corresponding configuration with two tapers 1.5, which are spliced as conical end pieces with the fiber-optic waveguide 1.2.
In ähnlicher Weise können auch Holmium-dotierte Festkör¬ perlaser sowie auch Festkörperlaser mit Frequenzvervielfa- chung im blauen und ultravioletten Spektralbereich und ge¬ pulste Gaslaser, wie z.B. Excimer-Laser und Stickstoffla¬ ser, realisiert werden.Similarly, holmium-doped solid-state lasers as well as solid-state lasers with frequency multiplication in the blue and ultraviolet spectral range and pulsed gas lasers, such as e.g. Excimer laser and nitrogen laser can be realized.
Es ist auch möglich, nur eines der Enden des Wellenleiters mit einem Taper-Koppler zu versehen.It is also possible to provide only one of the ends of the waveguide with a taper coupler.
In einer anderen Ausbildung des Erfindungsgedankens kann anstelle der optischen Faser auch ein planarer optischer Wellenleiter als Multipassreflexionsplatte zur Anwendung kommen. Eine Ausführungsform eines derartigen planaren Multipasswellenleiters 1.21 ist in Fig. 2a dargestellt. Wie in Fig. 2a zu erkennen ist, hat dieser Wellenleiter im wesentlichen die Gestalt eines flachen Quaders oder ei¬ ner Platte, der/die mit einem Ein-/Auskopplungsabschnitt 1.22 versehen ist und dessen große optische Weglänge durch vielfachen Strahldurchgang unter Reflexion an den Wandun¬ gen des Quaders realisiert wird.In another embodiment of the inventive concept, a planar optical waveguide can also be used as a multi-pass reflection plate instead of the optical fiber. An embodiment of such a planar multipass waveguide 1.21 is shown in FIG. 2a. As can be seen in FIG. 2a, this waveguide essentially has the shape of a flat cuboid or a plate which is provided with a coupling-in / coupling-out section 1.22 and the large optical path length of the beam by multiple beam reflection under reflection from the walls ¬ gene of the cuboid is realized.
Fig. 2b zeigt eine der in Fig. lb dargestellten Anordnung weitgehend entsprechende Ausbildung des optischen Teils des Lasersystems unter Verwendung eines Multipasswellen- leiters 1.21 der in Fig. 2a gezeigten Art anstelle des in Fig. lb dargestellten gewickelten Faser-Wellenleiters 1.2. Alle übrigen Elemente entsprechen denen der Fig. lb und werden daher nicht nochmals erläutert.2b shows a configuration of the optical part of the laser system which largely corresponds to the arrangement shown in FIG. 1b, using a multipass wave conductor 1.21 of the type shown in Fig. 2a instead of the wound fiber waveguide 1.2 shown in Fig. lb. All other elements correspond to those in FIG. 1b and are therefore not explained again.
Als Material für den planaren optischen Wellenleiter wer¬ den - je nach den Parametern der erzeugten Laserstrahlung - beispielsweise Chalkogenidgläser geeigneter Zusammenset¬ zung (z.B. Germanium-Arsen, Schwefel) oder im entsprechen- den Spektralbereich hochtransparente Kristalle, wie z.B. Saphir oder Yttrium-Aluminium-Granat oder sonstige Wirts¬ kristalle der jeweiligen Lasermedien oder z.B. auch Sili¬ zium, Germanium oder Zinkselenid, genutzt.Depending on the parameters of the laser radiation generated, chalcogenide glasses of a suitable composition (e.g. germanium arsenic, sulfur) or, in the corresponding spectral range, highly transparent crystals, such as e.g. Sapphire or yttrium aluminum garnet or other host crystals of the respective laser media or e.g. silicon, germanium or zinc selenide are also used.
Die Erfindung beschränkt sich in ihrer Ausführung nicht auf das vorstehend angegebene bevorzugte Ausführungsbei¬ spiel. Vielmehr ist eine Anzahl von Varianten denkbar, welche von der dargestellten Lösung auch bei grundsätzlich anders gearteten Ausführungen Gebrauch macht. * * * * * The embodiment of the invention is not limited to the preferred embodiment described above. Rather, a number of variants are conceivable which make use of the solution shown, even in the case of fundamentally different types. * * * * *

Claims

A n s p r ü c h e Expectations
1. Gütegeschaltetes Lasersystem, insbesondere für die Laserlithotripsie, mit einem laseraktiven Medium in einem Resonatoraufbau, einer Anordnung zum optischen Pumpen und einem passiven Güteschalter,1. Q-switched laser system, in particular for laser lithotripsy, with a laser-active medium in a resonator structure, an arrangement for optical pumping and a passive Q-switch,
d a d u r c h g e k e n n z e i c h n e t , daßd a d u r c h g e k e n n z e i c h n e t that
dem laseraktiven Medium eine Resonatorverlängerung zur Er¬ höhung der Laserimpulslänge zugeordnet ist, die einen op¬ tischen Wellenleiter aufweist.The laser-active medium is assigned a resonator extension for increasing the laser pulse length, which has an optical waveguide.
2. Gütegeschaltetes Lasersystem, insbesondere für die Laserlithotripsie, mit einem laseraktiven Medium in einem Resonatoraufbau, einer Anordnung zum optischen Pumpen und einem passiven Güteschalter,2. Q-switched laser system, in particular for laser lithotripsy, with a laser-active medium in a resonator structure, an arrangement for optical pumping and a passive Q-switch,
d a d u r c h g e k e n n z e i c h n e t , daßd a d u r c h g e k e n n z e i c h n e t that
die Anordnung zum optischen Pumpen so ausgebildet ist, daß das laseraktive Medium mit einer höheren als der zur Er- zeugung von Einzelimpulsen erforderlichen Pumpenergie an¬ geregt wird, um eine Kaskade von Impulsen (Burst) zu er¬ zeugen.the arrangement for optical pumping is designed in such a way that the laser-active medium is excited with a pump energy higher than that required to generate individual pulses in order to generate a cascade of pulses (burst).
3. Gütegeschaltetes Lasersystem nach Anspruch 1 oder 2, d a d u r c h g e k e n n z e i c h n e t , daß die ef- fektive optische Länge der Resonatorverlängerung so vorbe- stimmt ist, daß die Ausgangsstrahlung ein zeitlich und räumlich geglättetes Impulsprofil aufweist.3. Q-switched laser system according to claim 1 or 2, characterized in that the ef- The optical length of the resonator extension is predetermined so that the output radiation has a temporally and spatially smoothed pulse profile.
4. Gütegeschaltetes Lasersystem nach einem der vorange¬ henden Ansprüche, d a d u r c h g e k e n n z e i c h ¬ n e t , daß die effektive optische Länge der Resonator¬ verlängerung zur Erzielung einer Impulslänge im Bereich zwischen 0,2 und einigen μs wählbar ist.4. Q-switched laser system according to one of the preceding claims, d a d u r c h g e k e n n z e i c h ¬ n e t that the effective optical length of the Resonator¬ extension can be selected to achieve a pulse length in the range between 0.2 and a few microseconds.
5. Gütegeschaltetes Lasersystem nach einem der vorange¬ henden Ansprüche, d a d u r c h g e k e n n z e i c h - n e t , daß das laseraktive Medium einen Laserkristall, insbesondere aus Nd:YAG, Alexandrit oder Titansaphir oder einen solchen mit einer Er-Dotierung, aufweist.5. Q-switched laser system according to one of the preceding claims, that the laser-active medium has a laser crystal, in particular made of Nd: YAG, alexandrite or titanium sapphire or one with an Er-doping.
6. Gütegeschaltetes Lasersystem nach Anspruch 5, d a - d u r c h g e k e n n z e i c h n e t , daß der Laser¬ kristall doppelbrechende Eigenschaften aufweist, insbe¬ sondere aus Nd:YAl03 oder Nd:YLF besteht.6. Q-switched laser system according to claim 5, since - characterized in that the laser crystal has birefringent properties, in particular consists of Nd: YAl0 3 or Nd: YLF.
7. Gütegeschaltetes Lasersystem nach einem der Ansprüche 1 bis 4, d a d u r c h g e k e n n z e i c h n e t , daß das laseraktive Medium gasförmig ist, insbesondere ein Edelgashalogenid (Excimer oder Exciplex) aufweist. 7. Q-switched laser system according to one of claims 1 to 4, characterized in that the laser-active medium is gaseous, in particular a noble gas halide (excimer or exciplex).
8. Gütegeschaltetes Lasersystem nach einem der vorange¬ henden Ansprüche, d a d u r c h g e k e n n z e i c h ¬ n e t , daß der optische Wellenleiter eine in ihren Transmissionseigenschaften auf das laseraktive Medium abge¬ stimmte Lichtleitfaser aus Quarzglas, Chalkogenidglas oder Zirkonfluorid aufweist.8. Q-switched laser system according to one of the preceding claims, that the optical waveguide has an optical fiber made of quartz glass, chalcogenide glass or zirconium fluoride which is matched to the laser-active medium in terms of its transmission properties.
9. Gütegeschaltetes Lasersystem nach Anspruch 8, d a - d u r c h g e k e n n z e i c h n e t , daß die Licht¬ leitfaser eine Q/Q-Faser mit einer numerischen Apertur von 0,2 ist.9. Q-switched laser system according to claim 8, d a - d u r c h g e k e n n z e i c h n e t that the optical fiber is a Q / Q fiber with a numerical aperture of 0.2.
10. Gütegeschaltetes Lasersystem nach Anspruch 8 oder 9, d a d u r c h g e k e n n z e i c h n e t , daß die Lichtleitfaser an mindestens einem Ende mit einem ange- spleißten Taper versehen ist.10. Q-switched laser system according to claim 8 or 9, so that the optical fiber is provided with a spliced taper at at least one end.
11. Gütegeschaltetes Lasersystem nach einem der vorange¬ henden Ansprüche, d a d u r c h g e k e n n z e i c h ¬ n e t , daß der optische Wellenleiter einen gewendelten oder mäanderförmigen Aufbau zur Erreichung einer großen effektiven optischen Länge bei geringer Baulänge aufweist.11. Q-switched laser system according to one of the preceding claims, d a d u r c h g e k e n n z e i c h ¬ n e t that the optical waveguide has a coiled or meandering structure to achieve a large effective optical length with a small overall length.
12. Gütegeschaltetes Lasersystem nach einem der vorange¬ henden Ansprüche, d a d u r c h g e k e n n z e i c h - n e t , daß der optische Wellenleiter einen planaren Mul- tipasswellenleiter aufweist. 12. Q-switched laser system according to one of the preceding claims, characterized in that the optical waveguide has a planar multi-pass waveguide.
13. Gütegeschaltetes Lasersystem nach einem der Ansprü¬ che 2 bis 12, d a d u r c h g e k e n n z e i c h ¬ n e t , daß die Anordnung zum optischen Pumpen zur Abgabe einer um 30% oder mehr über der erforderlichen Pumpenergie liegenden Energie, insbesondere einer Energie im Bereich von 30 bis 50 J, ausgebildet ist.13. Q-switched laser system according to one of claims 2 to 12, characterized in that the arrangement for optical pumping for delivering an energy which is 30% or more above the required pump energy, in particular an energy in the range from 30 to 50 J, is trained.
14. Gütegeschaltetes Lasersystem nach einem der Ansprüche 2 bis 13, d a d u r c h g e k e n n z e i c h n e t , daß Mittel zum Anzeigen des Auftretens von Impulskaskaden vorgesehen sind.14. Q-switched laser system according to one of claims 2 to 13, d a d u r c h g e k e n z e i c h n e t that means for indicating the occurrence of pulse cascades are provided.
15. Gütegeschaltetes Lasersystem nach einem der Ansprüche 11 bis 14, d a d u r c h g e k e n n z e i c h n e t , daß die Resonatorverlängerung als Baugruppe, bestehend aus einer abberationsarmen Kolimationslinse, einer Faserwick¬ lung geeigneter Länge und einem konkaven Retroreflektor, aufgebaut ist.15. Q-switched laser system according to one of claims 11 to 14, so that the resonator extension is constructed as an assembly consisting of a low-aberration colimation lens, a fiber winding of suitable length and a concave retroreflector.
16. Gütegeschaltetes Lasersystem nach einem der vorange¬ henden Ansprüche, d a d u r c h g e k e n n z e i c h - n e t , daß das System als konfokale Anordnung mit einer Kollimationslinse und einem teildurchlässigen Konkavspiegel aufgebaut ist, wobei in der Strahltaille des Systems der passive Güteschalter angeordnet ist.16. Q-switched laser system according to one of the preceding claims, d a d u r c h g e k e n n z e i c h - n e t that the system is constructed as a confocal arrangement with a collimation lens and a partially transparent concave mirror, the passive Q-switch being arranged in the beam waist of the system.
17. Gütegeschaltetes Lasersystem nach Anspruch 16, a ¬ d u r c h g e k e n n z e i c h n e t , daß das System als Mittel zur Frequenzverdopplung einen in der Strahl¬ taille angeordneten Verdopplerkristall aufweist.17. Q-switched laser system according to claim 16, a ¬ characterized in that the system has a doubler crystal arranged in the beam waist as means for frequency doubling.
18. Gütegeschaltetes Lasersystem nach einem der vorange¬ henden Ansprüche, d a d u r c h g e k e n n z e i c h ¬ n e t , daß Mittel zum Erzeugen polarisierter Strahlung, insbesondere ein Polarisationsstrahlteiler und ein Retro- reflektor, vorgesehen sind.18. Q-switched laser system according to one of the preceding claims, d a d u r c h g e k e n n z e i c h ¬ n e t that means for generating polarized radiation, in particular a polarization beam splitter and a retro reflector, are provided.
19. Gütegeschaltetes Lasersystem nach einem der vorange¬ henden Ansprüche, d a d u r c h g e k e n n z e i c h ¬ n e t , daß das System aus drei, jeweils für sich vorju- stierten und einfach montierbaren, Baugruppen aufgebaut ist.19. Q-switched laser system according to one of the preceding claims, d a d u r c h g e k e n n z e i c h ¬ n e t that the system is constructed from three, each pre-adjusted and easy to assemble, assemblies.
* * * * * * * * * *
PCT/DE1994/000362 1993-03-27 1994-03-28 Q-switched laser system, in particular for laser lithotripsy WO1994023478A2 (en)

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US5963575A (en) 1999-10-05
DE4336947A1 (en) 1995-05-04
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ATE155617T1 (en) 1997-08-15
WO1994023478A3 (en) 1995-01-12
EP0691043B1 (en) 1997-07-16

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